The lon mutants of E. coli have pleiotropic effects on cell growth; (a) they are defective in the formation of septa between dividing cells after treatment with ultraviolet light and therefore form long filaments, (b) they overproduce the mucopolysaccharide coating of cells, possibly by disrupting the control of operons involved in synthesis of mucopolysaccharide, such as the gal operon, (c) they are defective in the degradation of abnormal proteins. We are investigating the genetic defect in the lon mutants with the aim of determining the interrelationships of these defects.